Electron tube mount including two electrodes supported on a common insulating header



United States Patent 0 ELECTRON TUBE MOUNT ENCLUDENG TWO ELEQTRODESUPPORTED ON A COMMON lNSULATlNG HEADER Carl Theodore Johnson, NewProvidence, lPa, assignor to Radio Corporation of America, a corporationof Delaware Filed Dec. 21, 1969, Sen No. 77,399 8 Claims. (Cl. 313--26d}The present invention relates to an electron tube mount having astructure for facilitating the assembling of the parts thereof in apredetermined order, and to an advantageous method of assembling theparts referred to.

One type of electron tube includes a mount comprising a header ofinsulating material on which are mounted in concentric relation adirectly heated cathode and a tubular grid having a plurality of siderods supporting a helix of lateral wire. The directly heated cathode mayhave a tubular structure constituted of a wire mesh, to the end portionsof which are affixed metal rings or end plates for connecting the endportions aforementioned to suitable lead-ins.

. Certain considerations involved in the aforementioned mount make itcritical that the parts thereof be mounted in a desired order. One ofthe major considerations is related to the cathode. One type of tubularmesh cathode is composed of wires that have been conditioned suitablyfor emission, prior to the assembly thereof in the mount. Suchconditioning may involve coating the wire with emitting material. Thecoating so produced is sensitive to relatively high temperatures priorto enclosure of the cathode in an evacuated envelope, and may be fatallyharmed if exposed to such temperatures.

However, the use of relatively high temperatures in assembling certainof the mount parts is unavoidable. Such high temperatures are required,for example, for fixing the lead-in members on which the end plates aremounted to walls defining an opening in the header. Where such header ismade of a ceramic such as aluminum oxide, the fixing operation involvesheating the header and lead-in members to a temperature suflicientlyhigh to fuse a metal coating on the aforementioned walls into fixedengagement with the lead-in members. to heating operation is usuallyperformed in an oven, as a consequence of which the end platessupporting the cathode and in turn supported by the lead-in members, arealso heated to the high temperature referred to. Such high temperaturewould have seriously harmed the cathode if it had been fixed to the endplates engaging the lead-ins prior to this heating operation.

The high temperatures referred to have also been required when'fixingthe grid side rods to walls of openings through a ceramic header. Suchfixing has also involved subjecting the header and grid to oventreatment. The problem of protecting a previously mounted cathode fromexcessive temperatures during this treatment is particularly serious,since practical manufacturing procedures require that the cathode bemounted prior to the mounting of the grid. The reason forthisrequirement is that once the grid is mounted, it shields the cathode tosuch extent as to render a subsequent mounting of the cathode difficultif not impossible, from a practical standpoint.

. Accordingly, it is an object of the present invention to provide amount having parts fixed by heat treatments and having a directly heatedoxide coated cathode free from harm by said heat treatments.

A further object is to provide an electron tube mount having a ceramicheader and a cathode support structure fixed to said header by arelatively high temperature treatment without harm to said cathode. 7

Another object is to provide an electron tube mount Patented Apr. 20,1965 comprising a tubular directly heated oxide coated cathode and atubular grid around the cathode mounted on a common ceramic header, withsaid cathode preserved from harm during the latter application ofrelatively high temperatures for fixing the grid to the header.

A further object is to provide a novel support for a grid to allow themounting of an oxide coated cathode on one face of a flat insulatingheader and the fixing of the grid to said header at a region spaced fromthe opposite face of said header, whereby the cathode is free from harmby the heat used in fixing the grid.

Another object is to provide a method of assembling the parts of anelectron tube mount having an oxide coated cathode, in a sequence topreserve said cathode from harm by relatively high temperatures used inthe assembling operation. 7 I

A further object is to provide a method of assembling the parts of anelectron tube mount comprising fixing at least one of said parts to afiat insulating header in a region disposed to one side of saidheadenand fixing another of said parts to said header in a regionappreciably spaced from the other side of the header to preserve saidfirst named part from heat used in fixing the second named part.

According to a structural feature of the invention, a mount sub-assemblyincluding a flat header of insulating material, is provided with acathode support structure extending from one face of theheader and agrid support in the form of a sleeve extending from the other face ofthe header and providing a region remote from the cathode support forfixing a grid to the sleeve. In this way it becomes possible to mount acathode on the support prior to the mounting of the grid on the header,since the region in which the grid is fixed is remote from the cathode.

According to a method aspect of the invention, an oxide coated cathodeis mounted in a position disposed to one side of a fiat insulatingheader and a grid is thereafter mounted on the header and surrounds thecathode and is fixed to the header by a support at a region spaced fromthe other side of the header, for protecting the cathode from heat usedin fixing the grid.

Further objects and features of the invention will become apparent asthe descriptionjproceeds.

In the accompanying drawing, to which reference is now made for adescription of one example of practicing the invention,

FIGURE 1 shows an elevation, partly in. section, of an electron tubemount in which the invention is embodied;

FIG. 2 is a bottom view of the mount shown in FIG. 1;

FIG. 3 is a fragmentary sectional view taken along the line 3-3 of FIG.1;

FIG. 4 is an exploded perspective view of parts constituting asub-assembly of'the mount in accordance with the invention; and 1 PEG. 5is an exploded perspective view of a sub-as sembly formed by the partsshown in FIG. 4, togetheri with certain other parts required to completethe mount structure shown in FIG. 1.

A more specific reference to the drawing will reveal that the electrontube mount shown in FIG. 1 comprises a header to, made of an insulatingmaterial such as a ceramic,fmade, for example, of aluminum oxide. On theheader iii are mounted a cathode structure 12 and a grid structure Thecathode structure 12 includes metalfend plates 16,

1% to which a directly heated tubular mesh cathode Zil is The fixedregions include endportions of the cathode ofrelatively small axialextent'thereby assuring a relatively large intermediate and activeportion of the cathode. The cathode mesh may comprise nickel wiressuitably conditioned for electron emission by an emitting arises? April20, 1965 c. T. JOHNSON 3,179,837

ELECTRON TUBE MOUNT INCLUDING TWO ELECTRODES SUPPORTED ON A COMMONINSULATING HEADER 2 Sheets-Sheet 2 Filed Dec. 21. 1960 INVENTOR. 0M1.Liam/50M ,47- ran Er United States Patent ELECTRON TUBE MOUNT WQLUDENGTWO ELECTRODES SUPIPORTED ON A COMMON INSULATING HEADER Carl Theodore.lohnson, New Providence, Pa, assignor to Radio Qorporation of America,a corporation of Delaware Filed Dec. 21, 196i Ser. I lo 773% 8 Claims.(Cl. 313-266) The present invention relates to an electron tube mounthaving a structure for facilitating the assembling of the parts thereofin a predetermined order, and to an a vantageous method of assemblingthe parts referred to.

One type of electron tube includes a mount comprising a header ofinsulating material on which are mounted in concentric relation :1directly heated cathode and a tubular grid having a plurality of siderods supporting a helix of lateral wire. The directly heated cathode mayhave a tubular structure constituted of a wire mesh, to the end portionsof which are affixed metal rings or end plates for connecting the endportions aforementioned to suitable lead-ins.

Certain considerations involved in the aforementioned mount make itcritical that the parts thereof be mounted in a desired order. One ofthe major considerations is related to the cathode. One type of tubularmesh cathode is composed of wires that have been conditioned suitablyfor emission, prior to the assembly thereof in the mount. Suchconditioning may involve coating the wire with emitting material. Thecoating so produced is sensitive to relatively high temperatures priorto enclosure of the cathode in an evacuated envelope, and may be fatallyharmed if exposed to such temperatures.

However, the use of relatively high temperatures in assembling certainof the mount parts is unavoidable. Such high temperatures are required,for example, for fixing the lead-in members on which the end plates aremounted to walls defining an opening in the header. Where such header ismade of a ceramic such as aluminum oxide, the fixing operation involvesheating the header and lead-in members to a temperature sufficientlyhigh to use a metal coating on the aforementioned walls into fixedengagement with the lead-in members. to heating operation is usuallyperformed in an oven, as a consequence of which the end platessupporting the cathode and in turn supported by the lead-in members, arealso heated to the high temperature referred to. Such high temperaturewould have seriously harmed the cathode if it had been fixed to the endplates engaging the lead-ins prior to this heating operation.

The high temperatures referred to have also been required when fixingthe grid side rods to walls of openings through a ceramic header. Suchfixing has also involved subjecting the header and grid to oventreatment. The problem of protecting a previously mounted cathode fromexcessive temperatures during this treatment is particularly serious,since practical manufacturing procedures require that the cathode bemounted prior to the mounting of the grid. The reason for thisrequirement is that once the grid is mounted, it shields the cathode tosuch extent as to render a subsequent mounting of the cathode difficultif not impossible, from a practical standpoint.

Accordingly, it is an object of the present invention to.

provide a mount having parts fixed by heat treatments and having adirectly heated oxide coated cathode free from harm by said heattreatments.

A further object is to provide an electron tube mount having a ceramicheader and a cathode support structure fixed to. said header by arelatively high temperature treatment without harm to said cathode.

Another object is to provide an electron tube mount "ice comprising atubular directly heated oxide coated cathode and a tubular grid aroundthe cathode mounted on a common ceramic header, with said cathodepreserved from harm during the latter application of relatively hightemperatures for fixing the grid to the header.

A further object is to provide a novel support for a grid to allow themounting of an oxide coated cathode on one face of a flat insulatingheader and the fixing of the grid to said header at a region spaced fromthe opposite face of said header, whereby the cathode is free from harmby the heat used in fixing the grid.

Another object is to provide a method of assembling the parts of anelectron tube mount having an oxide coated cathode, in a sequence topreserve said cathode from harm by relatively high temperatures used inthe assembling operation.

A further object is to provide a method of assembling the parts of anelectron tube mount comprising fixing at least one of said parts to afiat'insulating header in a region disposed to one side of saidheaden'and fixing another of said parts to said header in a regionappreciably spaced from the other side of the header to preserve saidfirst named part from heat used in fixing the second named part.

According to a structural feature of the invention, a mount sub-assemblyincluding a flat header of insulating material, is provided with acathode support structure extending from one face of the header and agrid support in the form of a sleeve extending from the other face ofthe header and providing a region remote from the cathode support forfixing a grid to the sleeve. In this way it becomes possible to mount acathode on the support prior to the mounting of the grid on the header,since the region in which the grid is fixed is remote from the cathode.

According to a method aspect of the invention, an oxide coated cathodeis mounted in a position disposed to one side of a flat insulatingheader and a grid is thereafter mounted on the header and surrounds thecathode and is fixed to the header by a support at a region spaced fromthe other side of the header, for protecting the cathode from heat usedin fixing the grid.

Further objects and features of the invention will become apparent asthe description proceeds.

In the accompanying drawing, to which reference is now made for adescription of one example of practicing the invention,

FIGURE 1 shows an elevation, partly in. section, of an electron tubemount in which the invention is embodied;

FIG. 2 is a bottom View of the mount shown in FIG. 1;

FIG. 3 is a fragmentary sectional view taken along the line 3-3 of FIG.1;

FIG. 4 is an exploded perspective view of parts constituting asub-assembly of the mount in accordance with the invention; and

FIG. 5 is an exploded perspective view of a sub-as sembly formed by theparts shown in FIG. 4, together with certain other parts required tocomplete the mount structure shown in FIG. 1.

A more specific reference to the drawing will reveal that the electrontube mount. shown in FIG. 1 comprises a Y header lit, made ofaninsulating material such as a ceramic, made, for example, of aluminumoxide. On the header 1% are mounted a cathode structure 12 and a gridstructure The cathode structure 12 includes metal end plates 16,

1% to which a directly heated tubular mesh cathode Zjtl is fixed. Thefixed regions include endportions of the cathode of'relatively sr nallaxial extent'thereby assuring a relatively large intermediate and activeportion of the cathode. The cathode mesh may comprise nickel wiressuitably conditioned for electron emission by an emitting coatingthereon, such as barium carbonate. The metal end plates 16, 13, may, forexample be made of nickel. Metal end plate 16 is supported on a metallead member 22 which may be made of an alloy known commercially as Kovarand containing iron, nickel and cobalt. The lead member 22 is sealedthrough the header in a vacuum tight bond. Lead member 22 passes throughan insulating sleeve 24 in the end plate 18, as shown in FIG. 3, toprovide electrical insulation between end plates l6, 13. End plate 18 isfixed to a lead member 26, which also may be made of Kovar and which issealed through the header ill in a vacuum tight manner. In a completedelectron tube, connection of lead member 26 and the exposedprong portion28 of the lead member 22, across a suitable power supply (not shown)will cause current to flow through the cathode to thereby raise it toemitting temperature. 7

The cathode 2% may be fixed to the end plates l6, 13 in one of severalways, including brazing, welding or by the application of a molten metalspray. Each of these ways of fixing requires access to the end portionsof the cathode from radial directions.

The grid structure 14 comprises a plurality, in the instant example six,side rods 3t) to 4-0, as shown fully in FIG. 3. The side rods may bemade of molybdenum and may have a thickness of .040 inch. Around theside rod array is disposed a helix 42 of grid lateral wire which may bemade of molybdenum and have a thickness of about 0.0l0 inch. The helixis suitably fixed to the side rods, as by being brazed thereto, forexample. The helix has an axial dimension substantially equal to that ofthe cathode 20 and overlaps the end portions of the cathode at which thecathode is fixed to the end plates 16, 18. The grid, therefore,precludes accessibility to the regions wherein the cathode is fixed tothe end plates referred to, from directions radially of the end platesand cathode.

A metal ring 44- is sealed to the periphery of the header Ill) in avacuum tight fashion, and has a flange 46 to which a metal envelope oranode (not shown) may be sealed for completion of an electron tube.

According to one feature of the invention, the grid 14, and the header10 are characterized by structure to permit a mounting of the grid onthe header, subsequent to the fixing of the cathode 259 to the endplates 16, 18 and without harm to the cathode. To this end, the header10 includes metal sleeves 43, Ed, 52 (FIG. 2) made for example, ofKovar, an alloy previously described. The sleeves are sealed to wallsdefining openings through the header 10, in a vacuum tight manner. Themetal sleeves are so arrayed about the axis of header 10, as to be inregister with alternate ones of the side rods, for a purpose to beexplained. Thus side rods 3t), 34, and 38 are in register with andextend through the sleeves 43, 5d, 52 respectively. Preferably, the siderods referred to extend slightly beyond the lower free ends of thesleeves as shown in FIG. 1 for rod and sleeve This provides an annularregion for accommodating a body of solder 54. The solder or brazingmaterial may be a composition known commercially as Nioro, and whichincludes nickel and gold. While this is a relatively high temperaturesolder (i.e. 900 C.) its disposition in the annular region referred tois sutficiently remote from the cathode 26, so that the latter is notharmed by the temperature used. The solder engages the free ends of thesleeves 4-8, 50, 52 and the sides of the end portions of the side rods30, 34, 33 threaded therethrough, in rugged bonds. The bonding regionaforementioned may be spaced about one-half inch from the adjacent faceof header 10, to assure the desired space isolation of this region fromthe cathode Ztl.

According to a method feature of the invention, the

assembling of the parts forming the cathode mount shown in FIG. 1, isaccomplished in two steps. The first step involves'assembling in fixedrelation, the parts shown in FIG. 4, to provide a subassembly of themount. In the fining openings 58, 6t 62, 64 and 66 are suitably providedwith a coating of molybdenum. The coating of molybdenum may be in turncovered by a relatively thin layer of a metal such as copper or metal,to facilitate a wetting of the parts extended into the openings and thepart engaging the periphery of the header 10, for promoting good seals.

The assembling of the parts shown in FIG. 4 may be aided by a suitablejig (not shown). Thus with the header it? supported on the jig, the ring44 may be telescoped over the header so as to engage the peripherythereof, the prongs 2-6, 23 of the cathode support structure 22 may beextended through openings 62, d5 of the header until the end plate 18rests on the upper surface of the header, and the sleeves 48, 5t), 52may be extended into openings 53, 6d, 64 so as to be flush with orextend slightly above the upper surface of the header as shown in FIGS.4 and 5, and to extend below the lower surface a distance of aboutone-half inch. In the example, the

header lltl had a diameter of one and one-half inches, andthe downwardlyextending portions of the sleeves 48, 5t had a length of one-half inch.When assembled as indicated, the parts are in snug engagement andseparated only by the coating or coatings before described. Theassembled relation is preserved, not only by the snug engagementreferred to, but by the jig (not shown) on which the parts are assembledand on which they rest.

The jig with the parts thus assembled thereon and supported thereby, isthen placed in an oven and subjected to a temperature of 820 C. forseven minutes. At this temperature, the outer coatings on the walls ofthe openings and on the periphery of the header lit become iuscd, andbond effectively to the sleeves d8, 56, 52 and the prongs 26, 28 of thecathode support structures, as well as to the sealing ring 44. Aftercooling, the jig and the sub-assembly thereon, which has now becomeintegrated, are removed from the oven. The sub-assembly is then removedfrom the jig and constitutes a subassembly 67 which is one of the partsdealt with in the second step of the method under consideration, asshown in FIG. 5.

Besides the sub-assembly 67, the second step of the method atfects thegrid structure 14 and the tubular mesh type cathode 2%). In carrying outthe second step, the mesh cathode 20 is first telescoped over the endplates 36, 18 of the cathode support structure 67, so that end portionsof the cathode engage the peripheries of the end plates referred to. Thetubular cathode it) has an inner diameter of .625 inch which issubstantially equal to the diameter of each of end plates 16, 18 so thatafter the telescoping operation, the cathode engages the end platessnugly. While so snugly engaged, the engaged end portions of the cathodeare fixed to the end plates in a suitable manner. One way in which thismay be accomplished is by sprying a molten metal such as molybdenum overthe end portions of the cathode so as to at least partly fillinterstices formed by the wires of the cathode. This at least partialfilling of the interstices bonds the end portions of the cathode to theperipheries of the end plates 16, 18.

After the cathode is fixed to the cathode support structure asdescribed, the grid structure 14 is telescoped over the cathode andoriented so that the longer side rods 30, 3d, 38 of the grid are inaxial register with sleeves 48, 50, 52 and enter the sleeves; When infully telescoped position, the shorter side rods 32, 36, 4% of the gridhave their lower ends, as viewed in FIG. 5, in abutment with referredto.

the upper surface of the header it). Such abutment desirably orients thegrid axially in the electrode mount shown in FIG. 1. The length of thelonger side rods 3d, 3d, 33 is such that when the foregoing abutmentoccurs, the longer side rods 39, 34, 33, extend slightly below the lowerends of the sleeves 48, 5t 52 as shown in FIG. 1, to permit convenientsolder bonding of the lower end portions of the sleeves and the longerside rods The sleeves 48, 5t 52 have an inner diameter for snuglyengaging the longer side rods aforementioned and an outer diameter forbeing engaged snugly in openings 58, 6t) and 64 in the header it It willbe noted from the foregoing that the lower end portions of the sleeves43, 50, 52 and the longer side rods 39', 34, 3-55 are appreciably spacedfrom the header 1% and the cathode fill. Furthermore, the solder 54- isapplied by localized heat, such, for example, as by dipping the lowerend portions of the sleeves and longer side rods into a pot of moltensolder. A better way of applying the solder, from-the standpoint of theamount of heat produced at the regions to be soldered, is to heat theend portion of each sleeve individually to soften the solder compositionpreviously deposited thereon, the heating being accomplished by aradio-frequency coil connected to a suitable power source and having adiameter for heating only one sleeve end portion. A plurality of coilsof this type may be used, to provide one coil for each sleeve, so as tosolder simultaneously the three sleeves to their associated grid siderods. However, it is preferred to employ only one coil, and tosuccessively heat the three sleeve ends to the melting point of thesolder. In this way the quantity of heat used at any one period of time,is reduced to a minimum and provides maximum assurance against heatdamage to the cathode.

This assunance against heat damage to the cathode is also n contributedto by the relatively low heat conductivity characteristic of the Kovaralloy of which the sleeves are composed.

The spacing of the end portions aforementioned of the sleeves and longerside rods from the header l0, and the localized character of the heatused in fixing the longer side rods to the sleeves, preserves theemission-conditioned cathode from harm during the fixing operation.

While the provision of side rods of ditterent length is utilized in thepreviously described example for properly localizing the lower endportions of the longer side rods for conveniently fixing such endportions to the sleeves described, this d-ilference in side rods lengthis also of advantage in mounting two concentric grids in such a way thatthe laterals thereof are in alignment transversely of the grid axis.This result canbe achieved by cutting the shorter side rod legs in theseveral grids so that the lengths thereof beyond the final turn of gridlateral wire are equal. in this way, the shorter side rods constitutereference means for desirable alignment of the turns of the severalgrids, and a fixing ofthe grids may be accomplished solely by the longergrid side rods.

While the atoredescribed method provides for assembling the cathode 2-0in the mount after the sub-assembly 66 (FIG. 5) has been fixed by ovenheating, this order in the assembling operation is dictated by the factthat, in the example described, the cathode was coated with emittingmaterial prior to the mounting of the cathode on the sub-assembly 6'3.Such prior application of the coating made it necessary to keep thecathode away from excessive heat, such as that involved in oven heatingthe sub-assembly 67.

However, it is feasible, according to the invention to defer applicationof the emitting coating to the cathode 2%, until after the cathode isassembled in sub-assembly 6'7. This permits the sub-assembly 67, withthe uncoated cathode 2d loosely mounted thereon, to be oven-heatedwithout damage toithe cathode. Besides fixing the elements ofsub-assembly 67 (FIG. 5) the oven heating may also beutilized for fixingthe uncoated cathode 2% to the end plates l6, 18 of the sub-assembly.This may be done by precoating the peripheries of the end plates with asuitable brazing material having a fusion point at the temperature ofthe oven. After the uncoated cathode 2-3 is thus fixed to thesub-assembly, the cathode may be suitably coated with emitting materialas aforementioned. An advantage of this modified method resides in thefact that the fixing of the elements of the sub-assembly 67, as well asthe cathode 2.49 may be efiected in a single heating operation.

It is, of course, necessary in either way of mounting the cathode 2%, todefer the mounting of the grid 14 until after the cathode has been fixedto the sub-assembly 67 and suitably coated with emitting material. Thisis for the reason that the grid, when positioned around the cathode,obstructs access to the cathode required for application of the emittingcoating.

What is claimed is:

1. An electron tube mount comprising a tubular electrode having at leasttwo support rods, a header made of insulating material and having ametal sleeve extending therethrough and beyond one face thereof forservice as a contact prong, said electrode extending from the other faceof said header, one of said support rods abutting against said otherface of the header, said one of said support rods being free to movelaterally of said header, the other of said rods extending through saidsleeve, and means fixing said other of said rods to an end portion only,of said sleeve remote from said header, said sleeve constituting thesole support means for said at least two support rods against lateralmovement with respect to said header.

2. An electron tube mount according to claim 1 and wherein said meansfor fixing comprises solder engaging the end of said sleeve extendingfrom said one face of the header and the free end portion of said otherof said rods.

3. An electron tube mount comprising a tubular cathode, a tubular gridin concentric relation to said cathode, an insulating header, meansengaging said header and supporting said cathode to one side of saidheader, said grid having a first side rod, a metal sleeve forming avacutight seal with and extending through said header and including aportion extending away from the other side of said header, said firstside rod extending through said sleeve, said grid having a second siderod in end butt relation to said. one side of said header, said firstand second rods having lengths to cause said first rod to extend beyondthe free end of said portion of the sleeve when said second rod abutsagainst said one side of the header, and means engaging the extendingportion of said first rod and said free end of said sleeve for fixingsaid grid to said header, said sleeve constituting the sole supportmeans for said first and second side rods against lateral movement withrespect to said header.

4. An electron tube mount comprising an insulating header havingopposite faces, a cathode support extending from one face of saidheader, a cathode fixed to said support only in regions spaced from saidone face, a tubular grid support sealed vacuum tight to and extendingfrom the other face of said header, and a grid having a side rodextending through and fixed to said grid support only in regions spacedfrom said other face, said cathode and grid being in concentricrelation, said grid having another side rod, said tubular grid supportconstituting the sole support means for said first named. side rod andsaid another side rod against lateral move- .ment with respect to saidheader.

5. An electron tube mount according to claim 4 and wherein said gridincludes two side rods of different length and wherein the shorter ofsaid side rods has an end in abutment with said one face of said headerfor fixing the adjacent end of the longer side rod in a position remotefrom said other face of ,said header.- H

6. A grid mount for an electron tube comprisingz' (A) a tubular gridhaving a plurality of parallel side rods,

(B) a plurality of grid wires extending transversely of and fixed tosaid side rods and forming an array terminating in a plane normal tosaid side rods,

(1) said side rods including end portions extending from said plane in adirection remote from said array,

(2) alternate ones of said end portions being of equal length, theothers of said end portions being of equal length and longer than saidalternate ones of the side rods,

(C) a flat insulating envelope header having openings extendingtherethrough,

(D) metallic sleeves hermetically sealed through said openings,

(1) said sleeves extending farther from one face of said header thanfrom the opposite face thereof,

(2) said others of said end portions extending through said sleeves andbeyond the end thereof extending from said one face of the header,

(3) said alternate ones of the end portions abutting against the otherface of said header,

(4) said other end portions being fixed only to said end of the sleeve,

(5) said sleeves constituting the sole means for supporting said gridagainst lateral movement with respect to said header.

7. A cathode-grid mount for an electron tube comprising:

(A) a fiat insulating envelope header,

(B) a tubular cathode having a coating of an emitting carbonate thereon,and fixed to and extending from one face of said header,

(C) a tubular grid positioned in concentric relation to said cathode andhaving a plurality of parallel side rods, said grid having an effectivearea terminating in a plane normal to said side rods,

(1) alternate ones of said side rods including portions extending fromsaid plane and away from said effective area,

(D) conductive sleeves hermetically sealed through said header andextending from the other face of the header,

(1) the others of said side rods being in end abutment with respect tosaid one face of the header,

(2) said portions of said alternate side rods extending through andbeing longer than said sleeves to cause end regions of said rod portionsto protrude from the ends of said sleeves remote from said other face ofthe header,

(E) and fixing means engaging said protruding end regions of saidalternate side rods and said ends of the sleeves, whereby said fixingmeans is spaced from said cathode to preserve the coating thereon fromharm by heat required to form the fixing means,

(F) said sleeves constituting the sole means for supporting said gridagainst lateral movement with respect to said header.

8. An electron tube mount comprising:

(A) an insulating header adapted to form a Wall portion of an electrontube envelope,

(B) a tubular grid mounted on one face of said header,

(C) an additional electrode mounted on said one face and closely spacedwith respect to said grid, said electrode being made of a material thatundergoes undesired chemical change when heated to a predeterminedtemperature,

(D) said grid including a plurality of side rods having one group ofadjacent ends thereof terminating in a plane normal to the side rods,

(1) said side rods having a second group of ends opposite to the firstgroup of ends,

(2) a first of said side rods having an end in said second group inabutment against said one face of the header,

(E) at least one metal sleeve hermetically sealed through said headerand including a major portion extending perpendicularly from the otherface of said header,

(1) and at least another of said side rods having a longer length thansaid first side rod and extending into said at least one sleeve to aregion thereof adjacent to the free end of said major portion of thesleeve,

(2) said at least another side rod being joined to said region in a bondformed at said predetermined temperature,

(3) said at least one metal sleeve being the sole support of said gridagainst lateral movement with respect to said header.

References Cited by the Examiner UNITED STATES PATENTS 2,161,005 6/39Bieling 313-261 X 2,485,668 10/49 Smyth 313-293 2,812,466 11/57 Murdock313-318 X 2,879,430 3/59 Wadia 313293 2,879,583 3/59 Booth et al 2925.132,935,782 5/60 Rangabeo 2925.13

JAMES D. KALLAM, Acting Primary Examiner.

RALPH G. NILSON, GEORGE N. WESTBY, DAVID J. GALVIN, Examiners.

3. AN ELECTRON TUBE MOUNT COMPRISING A TUBULAR CATHODE, A TUBULAR GRIDIN CONCENTRIC RELATION TO SAID CATHODE, AN INSULATING HEADER, MEANSENGAGING SAID HEADER AND SUPPORTING SAID CATHODE TO ONE SIDE OF SAIDHEADER, SAID GRID HAVING A FIRST SIDE ROD, A METAL SLEEVE FORMING AVACUUM TIGHT SEAL WITH AND EXTENDING THROUGH SAID HEADER AND INCLUDING APORTION EXTENDING AWAY FROM THE OTHER SIDE OF SAID HEADER, SAID FIRSTSIDE ROD EXTENDING THROUGH SAID SLEEVE, SAID GRID HAVING A SECOND SIDEROD IN END BUTT RELATION TO SAID ONE SIDE OF SAID HEADER, SAID FIRST ANDSECOND RODS HAVING LENGHTS TO CAUSE SAID FIRST ROD TO EXTEND BEYOND THEFREE END OF SAID PORTION OF THE SLEEVE WHEN SAID SECOND ROD ABUTSAGAINST SAID ONE SIDE OF THE HEADER, AND MEANS ENGAGING THE EXTENDINGPORTION OF SAID FIRST ROD AND SAID FREE END OF SAID SLEEVE FOR FIXINGSAID GRID TO SAID HEADER, SAID SLEEVE CONSTITUTING THE SOLE SUPPORTMEANS FOR SAID FIRST AND SECOND SIDE RODS AGAINST LATERAL MOVEMENT WITHRESPECT TO SAID HEADER.